CPU mining is done. GPU mining is still profitable though, for now.  The future is this: http://www.butterflylabs.com/

I would wait until the product is proven though, and then use an online mining calculator to estimate how long your break even ROI would be. That requires knowing your electricity costs and making some other assumptions which are very difficult at this point in time.

If you just want to mine for the fun of it, or to support the network, then of course all that number crunching won't be necessary.